This invention relates generally to roll-over protection structure for dump trucks, generally, and more particularly to a means for utilizing existing structure on dump trucks to enhance such roll-over protection.
Dump trucks of the off-highway type have a weight in and of themselves which approaches the payload, i.e., if the payload is 45 tons, then the empty weight of the vehicle will be approximately 72,000 pounds and fully loaded will be approximately 162,000 pounds. Providing roll-over protection for the cab has been a problem due to the weight of the vehicle and the resulting high loads encountered by any ROPS built into the cab itself. Conventionally, such dump trucks have been provided with a canopy on the dump truck which extends at least partially over the top of the cab, which canopy functions to protect the cab from being impacted by objects, such as large rocks etc. falling upon it during the loading of the dump body. Such canopies have therefore been structurally strong and securely affixed to the dump body and consequently could assist or complement any ROPS built into the cab. However, to function thusly the dump body and specifically the canopy secured thereto must remain in close proximity to the cab regardless of the orientation of the truck itself relative to the ground.
The dump bodies for such trucks are conventionally raised to their dump position by multi-stage hydraulic cylinders gravity being relied upon in some cases to return the dump bodies to their lowered transport position. With such arrangement there is almost total reliance upon gravity to hold the dump body in its lowered position, and in the event of a roll-over, it is obvious that the dump body may readily move away from its normal transport position in close proximity to an overlying cab. Even if a double acting cylinder were utilized to both raise and lower the dump body, it is highly likely that the integrity of hydraulic system would be damaged during such rollover, thereby causing the loss of positive pressure to hold the canopy in its protective position relative to the cab.
It is, therefore, an object of this invention to provide improved roll-over protection for an operator cab on a dump truck, particularly, through utilization of existing structures of the dump body.
It is also an object of this invention to provide such roll-over protection by assuring that the dump body is securely latched and will be maintained in its normal lowered position relative to the cab during a roll-over.
It is a further object of this invention to provide a latch for a dump body which is automatically engaged upon lowered of the body and is released only in response to initiation of the intentional pivoting of the dump body to its dump position.